Filter coefficient optimization apparatus, filter coefficient optimization method, and program

A filter coefficient optimization apparatus including an optimization unit that calculates an optimum value w* of a filter coefficient w={w1, . . . , wF} (wf(f=1, . . . , F, F is an integer equal to or more than 1) is a filter coefficient of a frequency bin f) of a beamformer that emphasizes sound (hereinafter referred to as target sound) from D sound sources (hereinafter referred to as a sound source 1, . . . , a sound source D),

• D being an integer equal to or more than 1,
• the optimization unit calculating the optimum value w* by performing derivation so as to reduce a difference in phase between adjacent frequency bins relevant to a response wfHaf,d(f=1, . . . , , F, d=1, . . . , D) of the beamformer in the frequency bin f for an angular direction θd,
• θd(d=1, . . . , D) being the angular direction in which a sound source d exists,
• af,d(f=1, . . . , F, d=1, . . . , D) being an array manifold vector in the frequency bin f corresponding to a sound wave that comes from the angular direction θd, the sound wave being a plane wave;
• and
• an output unit that sets the optimum value w* to the frequency bin of the beamformer and emphasizes at least a part of the sound wave as the target sound.

A filter coefficient optimization method including an optimization step in which a filter coefficient optimization apparatus calculates an optimum value w* of a filter coefficient w={w1, . . . , wF} (wf(f=1, F, F is an integer equal to or more than 1) is a filter coefficient of a frequency bin f) of a beamformer that emphasizes sound (hereinafter referred to as target sound) from D sound sources (hereinafter referred to as a sound source 1, . . . , a sound source D),

• D being an integer equal to or more than 1,
• the optimization step being a step of calculating the optimum value w* based on an optimization problem minwL(w) relevant to the filter coefficient w, under a predetermined constraint condition,
• L(w) being a cost function relevant to the filter coefficient w and being defined using a sum of a sum Σf=1FlMV_f(wf) of a cost function LMV_f(wf) and a predetermined regularization term,
• LMV_f(wf)=wfHRfwf(f=1, . . . , F) being a cost function relevant to the filter coefficient wf,
• Rf(f=1, . . . , F) being a spatial correlation matrix for sound other than the target sound relevant to the frequency bin f,
• the predetermined regularization term being defined using a difference in phase between adjacent frequency bins relevant to a response wfHaf,d(f=1, . . . , F, d=1, . . . , D) of the beamformer in the frequency bin f for an angular direction θd,
• θd(d=1, . . . , D) being the angular direction in which a sound source d exists, and
• af,d(f=1, . . . , F, d=1, . . . , D) being an array manifold vector in the frequency bin f corresponding to a sound wave that comes from the angular direction θd, the sound wave being a plane wave;
• and
• an output step that sets the optimum value w* to the frequency bin of the beamformer and emphasizes at least a part of the sound wave as the target sound.

A filter coefficient optimization method including an optimization step in which a filter coefficient optimization apparatus calculates an optimum value w* of a filter coefficient w={w1, . . . , wF} (wf(f=1, . . . , F, F is an integer equal to or more than 1) is a filter coefficient of a frequency bin f) of a beamformer that emphasizes sound (hereinafter referred to as target sound) from D sound sources (hereinafter referred to as a sound source 1, . . . , a sound source D),

• D being an integer equal to or more than 1,
• the optimization step being a step of calculating the optimum value w* by performing derivation so as to reduce a difference in phase between adjacent frequency bins relevant to a response wfHaf,d(f=1, . . . , F, d=1, . . . , D) of the beamformer in the frequency bin f for an angular direction θd,
• θd(d=1, . . . ,D) being the angular direction in which a sound source d exists, and
• af,d(f=1, . . . , F, d=1, . . . , D) being an array manifold vector in the frequency bin f corresponding to a sound wave that comes from the angular direction θd, the sound wave being a plane wave;
• and
• an output step that sets the optimum value w* to the frequency bin of the beamformer and emphasizes at least a part of the sound wave as the target sound.